Drive axle is an important part of automotive driveline, mainly consisting of the main reducer, differential, drive shaft and drive axle shell. As the name implies, the electric drive axle is driven by a motor drive axle. The electric drive axle is an important power transmission unit of the electric car, and the torque vectoring mechanism is the most important functional component of the electric drive axle with torque vectoring function. By controlling the motor and the planetary gear mechanism, it can achieve the torque coupling between the differential case and the drive shaft, hence enabling torque distribution between wheels.
Automotive differentials are the main components of the drive axle. Differentials function to transmit power to the left and right drive shafts of the car and at the same time allow the drive shafts rotating at different speed, in order to satisfy the wheels at both sides of the car as much as possible with the form of pure rolling, and hence reduce tire friction on the ground. When the car turns, the wheels at the outside of the corners are faster than those at the inside. A differential is arranged between the drive wheels at both sides of the vehicle to compensate for the different speed of the drive wheels. However, the conventional differentials usually evenly distribute torque between the driving wheels at both sides. In order to achieve optimum control of the vehicle, the drive wheels on the outside should output greater torque than that on the inside. In fact, increasing the torque applied on the drive wheel at the outside of the corners can promote and guide the vehicle in turn, which is particularly useful for high-speed cornering, and greatly reduces understeering, improves mobility and ultimate cornering ability, and increases driving fun. The differential of electric torque vectoring is an important configuration for luxury sports cars and SUVs.
In addition, the drive wheel may be on different roads with differential adhesion coefficient, namely the bisectional road. In this case, if the adhesive force of the drive wheel at one side is very small, for example on ice, the equal torque distribution characteristic of the conventional differential causes the wheel at this side acceleration skid, while the wheel at the other side with strong adhesion to the ground is unable to obtain sufficient driving force for running, then the car will break down and is unable to get off the hook. Of course, anti-slip differential can effectively avoid the low-speed break-down problem. However, when the car is on a good road and in high speed cornering, the anti-slip differential will make the wheels at both sides tend to have the same speed, and limit increase of the torque and speed of the outer wheel, which will lead to the insufficient cornering phenomenon, and limit the cornering ability of the vehicle.
Therefore, a new electric drive axle of torque vectoring is designed based on the structure of the drive axle with conventional bevel gear differential.